The laboratory directed by Morris Reichlin at the Oklahoma Medical Research Foundation, Oklahoma City, Ok., has been engaged in the study of autoimmune responses to RNAprotein antigens in SLE patients for over 20 years. Researchers have reported the initial descriptions of the Ro/SSA (Clark, G. M., Reichlin, M. and Tomasi, T. B. J. Immunol., 102:117-122 (1969)), La/SSB (Mattioli, M. and Reichlin, M. Arthritis Rheum., 17:421-429 (1974)), and nRNP(U.sub.1 RNP) 2. (Mattioli, M. and Reichlin, M. J. Immunol., 107:1281-1290 (1971)) systems, while others described the Sm antigen (Tan, E. M. and Kunkel, H. G. J. Immunol., 99:464-471 (1966)).
Over time, it has become apparent that certain profiles of anti-RNA protein antibodies are positively correlated with nephritis while other profiles are "negatively" correlated or "protected" from the development of serious renal disease. Thus, antibodies to nRNP(U.sub.1 RNP) alone were found to have a low frequency of nephritis (Sharp, G. C., et al. Am. J. Med., 52:148-159 (1972); Reichlin, M. and Mattioli, M. N. Engl. J. Med., 286:908-911 (1972)) while patients with both anti-nRNP and anti-Sm (or anti-Sm alone) had a high frequency of nephritis (Reichlin, M. and Mattioli, M. N. Engl. J. Med., 286:908-911 (1972); Maddison, P. J., et al. J. Rheumatol., 5:407-411 (1978)). In patients with anti-Ro/SSA alone, a high frequency of nephritis was noted (Wasicek, C. A. and Reichlin, M. J. Clin. Invest., 69:835-843 (1982); Hamilton, R. G., et al., Arthritis Rheum., 31:496-505 (1988); Harley, J. B., et al. Arthritis Rheum., 32(7):826-836 (1989)), while in those with both anti-Ro/SSA and anti-La/SSB, a low prevalence of nephritis was found. Studies of acid eluates from lupus nephritis kidneys have demonstrated enrichment of anti-Ro/SSA compared to serum levels (Maddison, P. J. and Reichlin, M. Arthritis Rheum., 22:858-863 (1979)), supporting the participation of Ro/SSA-anti-Ro/SSA complexes in the development and/or the perpetuation of the nephritis. Elution studies of antibodies to the U.sub.1 RNP/Sm complex also showed enrichment, but the precise specificities of these complexes (anti-Sm or anti-nRNP) were not determined because of technical limitations (Koffler, et al. J. Exp. Med., 134:294-312 (1971)). Serum levels of anti-Sm antibodies have been shown to fluctuate with disease activity (including nephritis) in some SLE patients (Barada, et al., Arthritis Rheum., 24:1236-1244 (1981)). These data indicate a role for the Ro/SSA and Sm systems in the development of nephritis, but only 50% of patients with either anti-Ro/SSA alone or anti-nRNP and anti-Sm (or anti-Sm alone) develop nephritis.
Much data support a major role for the DNA-anti-DNA system in the pathogenesis of lupus nephritis Clinical studies show that high serum anti-DNA levels correlate positively with the activity of nephritis, and that remissions are associated with declining anti-DNA levels (Harley, et al., Arthritis Rheum. (1989); Tan, et al. J. Clin. Invest., 45:1732-1740 (1966); Schur, P. H. and Sandson, J. N. Engl. J. Med., 278:533-538 (1982)). Anti-DNA has been shown to be enriched in serum cryoglobulins (Winfield, et al., J. Clin. Invest., 56:563-570 (1975)) and in acid eluates of lupus nephritis kidneys (Maddison and Reichlin (1979); Miniter, et al., Arthritis Rheum., 22:959-968 (1979); Beaulieu, et al. Arthritis Rheum., 22:565-570 (1979)). In all these studies, the specificity of these antibodies are to dsDNA (double stranded or native DNA).
Antibodies to native or ds DNA play a special role in the clinical diagnosis and pathology of Systemic Lupus Erythematosus (SLE). These 19, autoantibodies are highly specific, frequently correlate positively with disease activity (especially nephritis), and remissions are usually associated with declining anti-dsDNA levels (Hahn and Tsao, Antibodies to DNA. -Tn Dubois, Systemic Lupus Erythematosus. D-J. Wallace and B. H. Hahn, editors. (Lea and Febiger, Philadelphia, Pa. 1993) pp. 195-201; Harley, et al., Arthritis Rheum. 32:826-836 (1989); Tan, et al., J. Clin. Invest. 45:1732-1740 (1966); Schur and Sandson, N. Engl. T. Med. 278:533-538 (1982)). Patients who produce antibodies to the Ro/SSA and La/SSB (Harley, et al. (1989); Wasicek and Reichlin, J. Clin. Invest. 69:835-843 (1982); Hamilton, et al., Arthritis Rheum. 31:496-505 (1988); antigens as well as those that only have precipitins to U.sub.1 RNP (Sharp, Am. J. Med. 52:148-159 (1972); Reichlin and Mattioli, N. Engl. J. Med. 86:908-911 (1972)) very infrequently have anti-dsDNA in their serum and have a correspondingly low prevalence of nephritis. The mechanisms of these negative relationships of antibodies to Ro/SSA and La/SSB and U.sub.1 RNP with anti-dsDNA are not understood.
Studies have been reported in the literature describing differences in the ability of murine monoclonal antibodies to dsDNA to induce nephritis when hybridomas producing these antibodies are placed in normal mice (Tsao, et al. J. Clin. Invest., 85:530-540 (1990)). Others have shown that murine monoclonal antibodies penetrate cells, bind to nuclei, and induce glomerular proliferation and proteinuria in vivo (Vlahakos, et al., J. Am. Soc. Nephrol. 2:1345-1354 (1992)). Most recently, others have reported direct in vitro binding of murine monoclonal antibodies to glomeruli which is DNA dependent (DiValerio, et al., Clin. Res., 42:139A (1994)).
However, many questions remain about the mechanisms of lupus nephritis and especially the correlations that can be drawn from samples of the most accessible body fluid, the plasma. First, as many as 30% of lupus nephritis patients have never had measurable antibodies to dsDNA in their plasma. Second, as many as 25% of lupus patients with anti-dsDNA in their plasma do not develop nephritis even after many years. It is conceivable that in the first group of patients that anti-dsDNA is never detected in the plasma, because it is immediately complexed with antigen and deposited in the kidney and elsewhere. No one has studied the kidneys of such patients to see if there are large renal deposits composed of DNA and anti-DNA Some anti-DNA populations may not be nephritogenic because: (1) of poor complement fixing capacity (Miniter, et al., (1979) or Beaulieu (1979)), or (2) because they are largely IgM in nature (Pennebaker, et al. J. Clin. Invest., 60:1331-1338 (1977); Provost, et al., J. Invest. Dermatol., 74:407-412 (1980); Talal, et al., Clin. Exp. Immunol., 25:377-382 (1976)). These two latter observations may not be mutually exclusive, but systematic studies to assess their independent contributions when both are present have not been done. Other molecular factors that have been correlated with "pathogenicity" include high avidity, IgG isotype, high cationic charge, ability to precipitate with DNA, direct binding to glomeruli in vitro, and ability to bind DNA planted in glomerular structures. Thus, the presence of anti-DNA does not always lead to nephritis nor does its consistent absence in the plasma assure protection from serious nephritis. It may well be that lupus nephritis can develop in the absence of antibodies to dsDNA. What is clearly lacking in available diagnostic armamentarium is the ability to distinguish "pathogenic" from non-pathogenic antibodies. There are no simple "tests" at present that can distinguish "bad" from "good" or "harmless" anti-dsDNA antibodies.
It is therefore an object of the present invention to provide methods and reagents for assessment of pathogenicity of antibodies to double stranded (ds) DNA.
It is another object of the present invention to develop specific therapy based on anti-idiotypes to anti-dsDNA.